Thanks for the discussion and suggestions. I tested a number of glossy papers on the 4800 in my search for a Ciba-like print. I will relate my observations in case it might be helpful to others reading this post. I used one PS file for my test prints, a close-up fall foliage shot, predominately red, yellow and green (the sort I would like on Cibachrome).
For sheer glossy flatness of the surface, Pictorico HGF and Ilford Smooth High Gloss (not Smooth Gloss) clearly stand out and are indistinguishable to my eye (even at 10x magnification, the surfaces look identical). Unfortunately Pictorico is expensive and does not supply profiles (I used the UC ink profile and, to no surprise, the reds were redder and the blacks blacker). The Ilford SHG (also a polyester base) is half the price of Pictorico HGF but is only available in 8.5x11.
The remaining papers tried are: Epson Premium Glossy, Red River Ultra Gloss, Moab Kokopelli Gloss, Kodak Glossy and Ilford Smooth Gloss. I each case I used the manufacturer’s profile for the 4800. The Kodak paper yielded a darker and somewhat redder print than the others. The colors in the remaining papers are identical; I cannot identify the paper on the basis of color, quite a testament to inkjet technology. I can identify each paper, but only on the basis of surface texture. Each has a slight ripple in the surface that is unique. The ripple has the effect of reducing the perception of gloss differential. The Epson paper appears particularly effective at this. My conclusion: I would choose the Pictorico or Ilford SHG if the lighting is controlled to reduce GD, otherwise Epson or Red River, or really any of the others.